The Rondout Formation of New York State records two transgressive episodes, each represented by 20 ft of section, and each having occurred on a basin-wide scale as determined through correlation with equivalent units in Pennsylvania and central New York. The initial rate of each transgression was sufficiently rapid to allow the development of subtidal carbonate environments. As the rate of transgression slowed, the relative rate of sedimentation increased, allowing shoreline intertidal and supratidal environments to prograde into the line of section. The second transgressive episode was characterized by the development of a quartz sandstone barrier island-dolomite lagoon complex near shore and a coral-stromatoporoid biostromal environment offshore. Preservation of the bar ier was effected by the intertidal and supratidal sediments deposited during the progradational phase of sedimentation.

Geometrically, the sand body attains a thickness of 20 ft, a width of 0.5 mi, and scattered exposures occur through a length of 4 mi.

Internally, the sand body can be subdivided into a basal biosparite calcarenite, grading upward into a well churn-burrowed, fragmental fossiliferous quartz sandstone, a thin-bedded cross-stratified and burrowed quartz sandstone, and a medium-bedded, cross-stratified quartz sandstone. Grain size, bedding thickness, skeletal content, and structures change both laterally and vertically.

Paleocurrent data and the character of the sand body suggest that it developed through the southward longshore transport of sediment derived from both terrigenous and offshore-marine sources.

Recognition of the constructional and preservational history of the Fuyk Member has contributed to an understanding of the relation of this and other less well-preserved sandstone bodies (deposited during the same time interval in Pennsylvania and New York) to associated carbonate sediments and to the transgressions in general.

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